Researchers use DNA to direct assembly of FePO4 cathode material; close to 100% of theoretical storage capacity
EIA: US crude oil imports in 2011 dropped to lowest level since 1999 as domestic oil production rose

Copper-coated silicon particles as an anode material for Li-ion batteries

Long-term stability of specific discharge capacity for: (A) Cu-coated a-Si:H and (B) pristine a-Si:H.The theoretical charge storage capacity of graphite is given for comparison. Credit: ACS, Murugesan et al. Click to enlarge.

Researchers at the University of Texas at Austin have developed a scalable, chemical approach for synthesizing copper-coated hydrogenated amorphous silicon particles (Cu-coated a-Si:H) through a polyol reduction method for use as anode material in Li-ion batteries. (The presence of hydrogen in the a-Si:H particles facilitates Cu particle nucleation; the amount of hydrogen in the a-Si:H particles was found to significantly affect the amount of Cu deposition on the a-Si:H particles.)

In a paper published in the ACS journal Chemistry of Materials, they report that the copper coating of a-Si facilities (1) enhanced charge transfer kinetics and reduced charge transfer resistance, (2) highly reversible and increased charge storage capacity, and (3) improved tolerance to volumetric expansion/contraction processes upon cycling.

Different approaches have been explored to overcome the problem of volume expansion and contraction upon lithiation and delithiation of Si anodes. One approach is to use nanostructures, such as nanocrystals, nanowires, nanotubes or nanorods...Unfortunately, it is very difficult to produce these materials at a reasonable cost in the bulk quantities required for pragmatic applications. Additionally, decreasing the size and size dispersity of Si cannot alone effectively suppress specific volume changes or reduce particle-particle agglomeration.

An alternative approach to improve the stability of Si is by either forming an alloy with other ductile materials to act as a volumetric expansion buffer, or by using nanosized materials dispersed uniformly in a buffer matrix. The incorporation of buffer materials is advantageous as they reduce volumetric expansion and fracture during cycling. Typically, carbon materials have been used as the buffer material in different architectural configurations...However, in all of the above approaches, it is note well understood how ion and electron charge transfer kinetics are affected by addition of buffering agents with Si nanostructures, and whether the large irreversible capacity loss is caused by the Si material itself or by the buffering matrix holding the active material together.

...As the electrochemical lithiation/delithiation of crystalline Si leads to amorphorization in only a few cycles, some studies have explored the use of amorphous silicon (a-Si) for lithium ion battery applications, as there is no advantage to using crystalline Si. a-Si has other potential advantages over crystalline Si, including a smaller predicted volume expansion, shorter lithium ion diffusion lengths, and smaller charge transfer resistance. Nano-sized a-Si should offer even better tolerance to volume expansion/contraction processes.

—Murugesan et al.

The researchers prepared their electrodes by creating slurries of a-Si:H particles or Cu-coated a-Si:H as the active material, Super P carbon black as an electronic conductor, and PVDF dissolved in NMP as binder in a 70:20:10 ratio by weight. The 100% a-Si and carbon electrodes were made with 90:10 ratios of active materials and PBVDF dissolved in NMP as binder, respectively.

The resulting electrodes were used in coin cells (2032 type) using metallic lithium as the counter electrode and 1M LiPF6 dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio as the electrolyte. The team tested a-Si:H particles of varying sizes for electrochemical lithium insertion.

They found that the smallest a-Si:H particles tested (380 nm diameter) showed a relatively high capacity of 580 mAh g-1 in the first cycle that dropped significantly to 165 mAh g-1 in the second and then further to 40 mAh g-1 in subsequent cycles at a current rate of 100 mA g-1. Capacities of particles of different sizes differed by 10 to 20 mAh g-1 with no apparent size dependence. Average capacity was limited to about 50 mAh g-1. This storage capacity is quite low compared to the maximum storage capacity of 3,579 mAh g-1 of crystalline silicon, the team noted.

By contrast, the copper-coated a-Si:H particles showed a specific charge storage capacity of 600 mAh g-1 at 100 mA g-1 load—nearly 7 times higher than that of the pristine a-Si:H particles and higher than that of the theoretical capacity of graphite anodes (372 mAh g-1). The Cu-coated particles did not lose capacity and degrade with successive cycling; rather, they showed an increase in charge storage capacity with an increase in number of cycles.

Cu coated a-Si:H particles exhibited significantly enhanced lithium storage capacity over pristine a-Si:H particles of about 7 fold. The presence of Cu helps to suppress the solvent decomposition and enhance the lithiation/delithiation process taking place in a-Si:H particles and the role of the Cu layer in these processes. This chemical approach of coating Cu over a-Si:H particles shows great potential towards developing advanced anode materials for lithium ion batteries.

—Murugesan et al.


  • Sankaran Murugesan, Justin T. Harris, Brian A. Korgel, and Keith J. Stevenson (2012) Copper-coated Amorphous Silicon Particles as an Anode Material for Lithium-Ion Batteries. Chemistry of Materials doi: 10.1021/cm2037475



This technology seems to have the potential for the development of 500+ Wh/Kg long lasting batteries. It could give a welcomed boost to future PHEVs and BEVs.


All of these developments in battery technology seem great, but I wish the authors would make a statement about how exactly this new knowledge translates in a practical way to better, cheaper batteries on the commercial market (and in what time frame).



I am sure many of these advances will by synergistic in unforeseeable ways but they could at least state how each might contribute.

Are they just interesting or do they remove a roadblock?

There is a steady stream of them.

My enthusiasm for each breakthrough has evolved from "Great" to "So what?"


I am an EV fanatic and have HUGE hopes for BEVs.

But this stuff really does get me numb sometimes. I was just about to write what I was feeling but Toppa Tom beat me to it...nearly word for word what I was going to say.


You guys want to take all the fun out :)


Actually ChrisL beat me to it.

And note another one today, in the right hand column;
"Researchers use DNA to direct assembly of FePO4 cathode material; close to 100% of theoretical storage capacity. 19 March 2012" .


chris, toppa, dave,

Come on guys, you know better. All technical progress starts out this way, with fundamental research. And then these results get published in the scientific literature. Since that is what scientists do: publish.

Only a very small part of all scientific discoveries end up in a product. However the other 99% is not wasted money. They have helped increased the knowledge and understanding necessary to obtain the 1% successful ideas.

If these scientific publications upset you, then I suggest you stop reading and just wait for the cars to appear in the showrooms.


Anne -
I agree with everything you say about scientific research. I also like reading about all this battery progress -- it doesn't upset me; my next car will absolutely be a BEV, but I would like it to have a lighter battery. But I think these researchers must have an inkling of why their work is important toward building a better battery, and I would love for them to share that insight in language that those of us not working in the field can understand. Just a sentence or two would help a lot.


I thought the primary advantage was apparent from the graph: increased energy density. I'm glad when the results are so positive that they don't have to justify themselves with hopes and wishes marketing.


Let's not give up (too fast) on high performance lower cost batteries and super and ultra caps.

UCLA has very recently found ways to produce much lower cost, very high performance, ultra caps using easily made low cost graphene flexible electrodes.

Those ultra caps have 15 to 20 times higher performance than current super caps, have a power density of almost 3 order of magnitude better than current lithium batteries while matching their best energy density. The new ultra caps are very resistant to shock and vibration and can be quickly charged and discharged many thousand times.

The same low cost graphene electrodes could also improve lithium batteries performance up to 10 times.

The future of ultra caps and batteries is very bright.

Together with better batteries and better ultra caps will come better lower cost BEVs.

Bob Wallace

Envia has an independent lab-tested lithium battery that holds 3x the amount of power of current EV batteries and can be manufactured for half the cost. At least 1,000 cycles and calendar life is looking good.

They might be quick to market because they don't intend to become manufacturers but to license their technology to existing battery makers. And we've got a whole bunch of new EV battery plants in the US, thanks to the economic stimulus recovery money.

I think we could see much better, cheaper batteries in about two years.


Lots of good work being done on batteries, but the one pacing item is customer acceptance of EVs. One article comment said that EVs need many more chargers than engine cars need fueling stations.

THAT is the key point. If you get enough batteries, they cost and weigh too much. If you do not have enough, there is not enough range. This is not a problem with liquid fueled cars. Maybe one has a 300 mile range and another has a 400 mile range, but the car with the larger tank is not twice the price.


SJC...a very well known gentleman recently said that 'you cannot teach right-wing pundits and die-hard the truth'. Since they will probably die
before they change their mind, it is better to let them be and concentrate your efforts on the other 50%.

Let's hope that their children will be more reasonable and rational.


I hope EVs do well, but I am not willing to put all my options for a more secure future in that faith.

Faith is belief without proof, that is why they call it faith. I would hope we are all rational logical people on here and are more convinced by the facts than evangelical rhetoric.


There is another way.

A French biochemist, Pierre Calleja, has designed a micro algae street lamp that consumes about 2 tonnes of CO2/year. That's equivalent to planting 200 new trees. Three or four such lamps would consume the CO2 emissions of an average ICEV. Hummer users could install 12 to 16 lamps in their yards and porches an absorb most of the CO2 emissions they created.


You get more benefit from the same number of batteries if you put smaller numbers of them into greater numbers of vehicles, e.g. hybrids and plug-in hybrids.

If you're putting between 500 Wh and 2 kWh of batteries into the typical vehicle, the weight and bulk isn't really an issue.

HarveyD this early stage of development, batteries with very large energy storage capabilities (30 to 100 Kwh) are not practical because they are too heavy and too expensive. The same could have been said about 400+ hp ICE 120 years ago.

Future batteries will eventually become 10 times smaller, weight 10 times less and cost 10 times less per Kwh. A 100 Kwh pack will become as common as today's 10 Kwh pack. We may be half way there by 2020/2022 and most of the way there by 2030/2035. It is just a question of time, priority and resources used.


The bulk and weight are already not the issue, it's cost. Part of the problem is that as of yet no one is building the efficient, aerodynamic platform that would allow 200-300 miles of range from a reasonable sized cost effective pack. Tesla can do it with an 85kWh pack and an $80k vehicle, but a more reasonably sized and shaped glider could get similar range with a much smaller pack using existing chemistry. Cell level improvements will help but much more could be done with what we have right now.

The comments to this entry are closed.